1. Field of the Invention
The present invention relates to a method of assembling a spool valve, and more particularly to a method of assembling a spool or a spring into a valve hole drilled in a valve body. The present invention also relates to a method for checking the state of the spool and spring thus assembled.
2. Description of the Prior Art
A plurality of spool valves are incorporated as secondary valves for an automatic transmission in an automobile. For each spool valve, the clearance between a spool and a valve hole is extremely small. Therefore, it is difficult to automate the step of inserting the spool into the valve hole. A known automatic valve assembling apparatus is disclosed in, for example, Unexamined Japanese Pat. applications Laid Open Nos. 123231/1985 and 26432/1991. In a known application, one end of a spool held inside a magazine or a guide member is opposed to a valve hole opened on a valve body and, by vibrating the valve body, the spool is engaged from the magazine or the guide member into the valve hole by gravity.
However, in the conventional methods, a mechanism to vibrate the entire valve body is required. As a result, the entire structure of the apparatus becomes disadvantageously complicated and larger, and there is a higher equipment cost. In addition, when long and short springs are mounted before the spool is mounted, it may possibly occur that mounting of the spool is disturbed by interference with the spring.
Furthermore, where a plurality of spools and springs in different dimensions are sequentially assembled, a checking procedure for confirming that they are assembled normally is indispensable to prevent assembling errors. According to conventional systems, however, such a checking procedure must be performed visually by an operator. Consequently, automation of the checking procedure has been desired.